Television receiver having a sound-signal detector electrode in its picture tube



y 1956 .J. E. ROBINSON 2,744,954

TELEVISION RECEIVER HAVING A SOUND-SIGNAL DETECTOR ELECTRODE IN ITS PICTURE TUBE OriginalFiled Jan. 3, 1948 Fig.

HORIZONTAL /49 DRIVE VERTICAL I DRIVE AMPLIFIER DETECTOR l 52 R 5| l 50 AUDIO AMPLIFIER 54 INVENTOR. JAMES E. ROBINSON ATTORNEYS United States Patent TELEVISION RECEIVER HAVING A SOUND-SIG- NALEDETECTOR ELECTRODE IN ITS PICTURE TUB James E. Robinson, Eggertsville, N. Y., assiguor to American Optical Company, Southbridge, Mass, a voluntary association of Massachusetts 4 Claims. (Cl. 178--5.8)

This invention relates to a system for separating and obtaining sound-representative pulses from a television signal which contains both video signals and pulsed sound signals.

An object of the invention is to provide a structure for separating and utilizing video signals and sound-pulse signals, from a combined video and sound-pulse input signal. Other objects will be apparent.

'In the drawing,

Fig. 1 is a graphical representation of the combined video and sound-pulse input signal used in the invention,

Fig. 2 shows a receiving cathode ray tube structure and circuits for separating and utilizing the video and soundpulse signals, and

Fig. 3 shows a preferred structure of the picture screen on the cathode ray tube.

The signal of Fig. 1 may be produced in a manner described in the parent patent application, Serial No. 460, and comprises synchronizing pulses x, sound pulses y, and video signals z. The sound pulses y are width-modulated in accordance with desired sound signals, and are of uniform amplitude.

The tube 300 which both reproduces the picture and separates out the sound pulses is shown in Fig. 2. It has all the parts of an ordinary picture-reproduction tube such as the type called a kinescope except that its fluorescent screen 301 does not extend all the way across its outer end. At one side of the fluorescent screen is a long narrow aperture box 302 containing a long slit 314 in its inner face. The box is made of low-emission material such as metal coated with graphite. Within the box and insulated therefrom is a signal strip 303 of silver, aluminum or other high-emission material. A co-axial cable 350 extends out through the envelope of the tube having its inner conductor 351 connected to the signal strip 303 and its outer conductor 352 connected to the aperture box 302 and grounded by a connection 216. The tube is provided with a band 318 between the ordinary anode band 313 and the aperture box, and this band is maintained at a positive potential such as 250 volts.

When the tube is connected as shown in Figure 2 so that its electron stream is modulated by the combined sound-and-picture signal, and scans the fluorescent screen 301, a centering device 319 connected to the horizontal deflecting plates 307 is adjusted so that the electron stream enters the slit 314 in the box 302 and strikes the signal plate 303 during the brief portion of each sweep in which it is modulated by a sound pulse and strikes the fluorescent screen 301 during the remainder of its travel.

The separated sound pulses received on the signal plate 303 are carried to the sound-reproducing circuit 50-52 by an output circuit 304 which includes the inner conductor 351 of the co-axial cable 350. A positive voltage of about 250 volts is applied to the signal plate 303 by connecting the resonant circuit 50 to a source of potential.

In a picture-reproducing tube, the electron stream creates irregular static charges on the fluorescent screen and the glass and there is considerable electron splatter "ice from the screen. It is extremely diflicult to prevent these effects of the stream from causing irregular voltage variation on the signal strip 303. Such voltage variation would, of course, prevent reception of the sound in pure form. By the arrangement illustrated, I have succeeded in protecting the signal strip 303 from such interference. Several features contribute to this important result. The acceleration of the stream by the voltage applied to the band 318 assists in causing rapid passage of the electrons through the slit 314 in the box 302 when the stream is directed towards this slit. The box prevents electron splatter from striking the signal strip 303. Charges produced on the box by such splatter are immediately drawn ofi to ground through the connection 216. This ground con nection serves also to draw off some of the static charges on the glass, since the outer conductor 352 of the co-axial cable is in direct contact with the glass. Furthermore, in the case of a picture tube in which the fluorescent screen 301 is covered by a so-called metallic mirror layer 301a (Fig. 3), the electrostatic charges on this layer are also drawn off through the outer conductor 352 and the ground connection 216. When such a mirror layer 301a is grounded by this means, it has the advantage of largely reducing the irregular electrostatic charges which would otherwise be built up on the fluorescent screen, and thus aids in preventing any extraneous voltage effects on the signal plate 303.

The video signals z and sound pulses y are fedto the control electrode 306 by the video amplifier 45. The video signals 2 cause a picture to appear on the screen 301. The sound pulses y, separated from the combined signal by the signal strip 303, is fed through the audio circuits 50-53 and to the loudspeaker 54, as is more fully described in co-divisional patent application Serial No. 76,168, filed February 12, 1949.

This application is a division of my application Serial No. 460, filed January 3, 1948, as a continuation-in-part of my application Serial No. 712,264, filed November 26, 1946. Another divisional application, Serial No. 345,961, was filed March 31, 1953.

While a preferred embodiment of the invention has been shown and described, various modifications will appear to those skilled in the art, which will fall within the scope of invention as defined in the claims.

What I claim is:

1. The combination with a picture-reproducing cathode ray tube containing a fluorescent screen and a cathode ray source, of means for separating out sound pulses from a combined sound and video signal comprising means to modulate the intensity of said ray in accordance with said combined signal, a metal signal strip positioned near one vertical edge of said fluorescent screen means for deflecting said ray horizontally and vertically so that all of the horizontal deflections of said cathode ray cross said strip, a, shield of conducting low emission material surrounding said strip and containing a slit through which the cathode ray may strike the strip when said pulses occur, a coaxial cable extending through the envelope of the tube with its outer conductor in contact with the glass of the tube and connected to the shield and its inner conductor connected to the strip, an output circuit connected to the inner conductor, and an independent circuit connected to the outer conductor and providing a path to ground.

2. The combination with a picture-reproducing cathode ray tube containing a fluorescent screen and a cathode ray source, of means for separating out sound pulses from a combined sound and video signal comprising means to modulate the intensity of said ray in accordance with said combined signal, a metal signal strip positioned near one vertical edge of said fluorescent screen means for deflecting said ray horizontally and vertically so that all of the horizontal deflections of said cathode ray cross said strip,

a shield of conducting low emission material surrounding said strip and containing a slit through which the cathode ray may strike the strip when sound pulses occur, an anode band in said tube between said deflecting means and said strip, another band in the tube. between said anode band and said strip, an output circuit connected to the signal strip, an independent circuit connected to the shield and providing a path to ground, and means for applying a positive potential to the signal strip and to said other band.

3. The combination with a picture-reproducing cathode ray tube having a fluorescent screen and metallic mirror layer covering the screen and having a cathode ray source, of means for separating out sound pulses from a combined sound and video signal comprising means to modulate the intensity of said ray in accordance with said combined signal, a metalsignal strip positioned near one vertical edge of the fluorescent screen and mirror layer means for deflecting said ray horizontally and vertically so that all of the horizontal deflections thereof cross said strip when said sound pulses occur, a co-axial cable extending through the envelope of the tube with its outer conductor in contact with the glass of the tube and the mirror layer and its inner conductor connected to the strip, an output circuit connected to the inner conductor, and an independent circuit connected to the outer conductor and providing a path to ground.

4. In a cathode ray tube for television reception of sound and video signals, a picture reproducing screen, a source of an electron beam, deflection means for sweeping said beam horizontally and vertically, means for modulating the intensity of said beam in accordance With said sound and video signals, and a sound pickup structure positioned adjacent an edge of said screen so as to be scanned bythe horizontal deflections of said beam, said structure comprising a conductive signal strip, a conductive shield shaped and positioned to substantially surround said signal strip, an aperture in said shield positioned on a side thereof substantially facing said source of an electron beam and exposing said signal strip to said electron beam when traversed horizontally thereby, means for causing said sound signals to occur when said beam traverses said strip, a first lead conductor connected to said signal strip and extending to the outside of said cathode ray tube, and a second lead conductor connected to said shield and extending to the outside of said cathode ray tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,036,350 Montani Apr. 7, 1936 2,146,876 Zworykin Feb. 14, 1939 2,159,529 Langenwalter et al. May 23, 1939 2,195,676 McCarthy Apr. 2, 1940 2,212,645 Morton Aug. 27, 1940 2,361,766 Hadekel Oct. 3-1, 1944 2,405,252 Goldsmith Aug. 6, 1946 2,409,488 Homrighous Oct. 1-5, 1946 2,452,157 Sears Oct. 26, 1948 2,462,860 Grieg Mar. 1, 1949 2,492,344 Adams et a1 Dec. 27, 1949' 2,523,162 Sunstein Sept. 19, 1950 2,537,991 Grieg Jan. 16, 1951 2,624,797 Lawson et al. Jan. 6, 1953 FOREIGN PATENTS 503,087 Great Britain Mar. 30, 1939 565,511 Great Britain Oct. 2, 1944 612,135 Great Britain Nov. 9, 1948 

